Nikikai is a voluntary group of vocalists formed in 1952. It was included in the "Nikikai Opera Promotion Association" in September 2005 and does not exist as an independent organization.

The current "Nikikai" refers to the vocal member organization of the "Tokyo Nikikai", and the members are called "Nikikai members". The "Nikikai Opera Promotion Association" was established in 1977 and changed its name to "Tokyo Nikikai" in October 2005.